The Curtiss JN-4 "Jenny" was one of a series of "JN" biplanes built by the Curtiss Aeroplane Company of Hammondsport, New York, later the Curtiss Aeroplane and Motor Company. Although the Curtiss JN series was originally produced as a training aircraft for the U.S. Army, the "Jenny" (the common nickname derived from "JN") continued post-World War I as a civil aircraft as it became the "backbone of American postwar [civil] aviation." Thousands of surplus Jennys were sold at bargain prices to private owners in the years after the war and became central to the barnstorming era that helped awaken America to civil aviation through much of the 1920s.
The JN-2 was an equal-span biplane with ailerons controlled by a shoulder yoke located in the aft cockpit. It was deficient in performance, particularly climbing, because of excessive weight. The improved JN-3 incorporated unequal spans with ailerons only on the upper wings, controlled by a wheel. In addition, a foot bar was added to control the rudder.
Curtiss JN-3, the progenitor of the JN-4, deployed to Mexico, c. 1916
The 1st Aero Squadron of the Aviation Section, U.S. Signal Corps received eight JN-2s at San Diego in July 1915. The squadron was transferred to Fort Sill, Oklahoma, in August to work with the Field Artillery School, during which one JN-2 crashed with a fatality. The pilots of the squadron met with its commander, Capt. Benjamin Foulois, to advise that the JN-2 was unsafe because of low power, shoddy construction, lack of stability, and overly sensitive rudder. Foulois and his executive officer Capt. Thomas D. Milling disagreed, and flights continued until a second JN-2 crashed in early September resulting in the six remaining JN-2s being grounded until mid-October when two new JN-3s were delivered and the grounded aircraft had been upgraded to the new design. In March 1916, these eight JN-3s were deployed to Mexico for aerial observation during the Pancho Villa Expedition of 1916–1917.
After the successful deployment of the JN-3, Curtiss produced a development, known as the JN-4, with orders from both the US Army and an order in December 1916 from the Royal Flying Corps for a training aircraft to be based in Canada.[N 1] The Canadian version was the JN-4 (Canadian), also known as the "Canuck", had some minor differences from the US version, including a lighter airframe, ailerons on both wings, a bigger and more rounded rudder, different shaped wings, stabilizer, and elevators.
Curtiss JN-4Ds at Camp Taliaferro, Texas, c. 1918
The Curtiss JN-4 is possibly North America's most famous World War I aircraft. It was widely used during World War I to train beginning pilots, with an estimated 95% of all trainees having flown a JN-4. The U.S. version was called "Jenny", a derivation from its official designation. It was a twin-seat (student in front of instructor) dual control biplane. Its tractor prop and maneuverability made it ideal for initial pilot training with a 90 horsepower (67 kW) Curtiss OX-5V8 engine giving a top speed of 75 miles per hour (121 km/h) and a service ceiling of 6,500 feet (2,000 m). The British used the JN-4 (Canadian), along with the Avro 504, for their primary World War I trainer using the Canadian Aeroplanes Ltd. indigenous variant. Many Royal Flying Corps pilots earned their wings on the JN-4, both in Ontario and later in winter facilities at Camp Taliaferro, Texas.
Although ostensibly a training aircraft, the Jenny was extensively modified while in service to undertake additional roles. Due to its robust but easily adapted structure able to be modified with ski undercarriage, the Canadian Jenny was flown year-round, even in inclement weather. The removable turtle-deck behind the cockpits allowed for conversion to stretcher or additional supplies and equipment storage, with the modified JN-4s becoming the first aerial ambulances, carrying out this role both during wartime and in later years. Most of the 6,813 Jennys built were unarmed, although some had machine guns and bomb racks for advanced training. With deployment limited to North American bases, none saw combat service in World War I.
The Curtiss factory in Buffalo, New York, was the largest such facility in the world, but due to production demands, from November 1917 to January 1919, six different manufacturers were involved in production of the definitive JN-4D. Production from spare or reconditioned parts continued sporadically until 1927, although most of the final orders were destined for the civil market in Canada and the United States.
One of the many daredevil stunts performed by JN-4 pilots was to work with a "wingwalker".
Like the re-engined JN-4H version of the most-produced JN-4 subtype, the final production version of the aircraft was the JN-6, powered by a Wright Aeronautical license-built 150 hp (112 kW) Hispano-Suiza 8 V-8, first ordered in 1918 for the US Navy. A floatplane version was built for the Navy which was so modified that it was essentially a different airframe. This was designated the N-9. In U.S. Army Air Service usage, the JN-4s and JN-6s were configured to the JNS ("S" for "standardized") model. The Jenny remained in service with the US Army until 1927.
After World War I, thousands were sold on the civilian market, including one to Charles Lindbergh in May 1923 in which he then soloed. Surplus US Army aircraft were sold, some still in their unopened packing crates, for as little as $50, essentially "flooding" the market.[N 2] With private and commercial flying in North America unhampered by regulations concerning their use, pilots found the Jenny's slow speed and stability made it ideal for stunt flying and aerobatic displays in the barnstorming era between the world wars, with the nearly identical Standard J-1 aircraft often used alongside it. [N 3] Some were still flying into the 1930s.[N 4]
Between 1917 and 1919 the JN-4 type accounted for a number of significant aviation "firsts" while in service with the US Army Signal Corps Aviation Section and the United States Marine Corps (USMC) including flying the first U.S. Air Mail in May 1918.
In a series of tests conducted at the U.S. Army's Langley Field in Hampton, Virginia, in July and August 1917, the world's first "plane-to-plane" and "ground-to-plane, and vice versa" communications by radiotelephony (as opposed to radiotelegraphy which had been developed earlier) were made to and from modified US Army JN-4s[N 5] by Western Electric Company (Bell Labs) design engineers Lewis M. Clement and Raymond Heising, the developers of the experimental wind generator powered airborne wireless voice transmitter and receiver equipment.
In early 1919, a United States Marine Corps (USMC) JN-4 was also credited with what is believed to be the first aircraft to successfully execute a "dive bombing" attack during the United States occupation of Haiti. Marine Corps pilot Lt Lawson H. Sanderson mounted a carbine barrel in front of the windshield of his JN-4 (previously, an unarmed trainer that had a machine gun mounted in the rear cockpit) as an improvised bomb sight that was lined up with the long axis of his aircraft, loaded a bomb in a canvas mail bag that was attached to the JN-4's belly, and launched a single-handed raid at treetop level, in support of a USMC unit that had been trapped by Haitian Cacos rebels. Although the JN-4 almost disintegrated in the pullout, the attack was effective and led to Sanderson in 1920 developing further pioneering dive-bombing techniques to provide Marine pilots with close aerial support to infantry comrades.
A JN-4 C227 "Canuck" (USAAS #39158) operated by the US Air Army Air Service in 1918, is now restored and on display at the Canada Aviation and Space Museum.
The most radical development of the Curtiss JN-4 was the Twin JN (or "Twin Jenny") in limited production and service with the US military.
Although the first series of JN-4s were virtually identical to the JN-3, the JN-4 series was based on production orders from 1915–1919.
JN-4A — Production version of the JN-4, 781 built.
JN-4B — This version was powered by an OX-2 piston engine, 76 built for the U.S. Army, nine for the U.S. Navy.
JN-4C — Experimental version, only two were built.
JN-4 (Canadian) Canuck — Canadian-built version, 1,260 built by Canadian Aeroplanes Ltd. for the RFC in Canada/RAF in Canada and USAAC. Independently derived from the JN-3, it had a lighter airframe, ailerons on both wings, a bigger and more rounded rudder, different shaped wings, stabilizer, and elevators. Its use by the USAAC was curtailed as the lighter structure was claimed to cause more accidents than the US built aircraft, although no air fatalities were attributed to the structural integrity of the type.
JN-4D — Improved version, adopting the control stick from the JN-4 (Canadian) 2,812 built.
JN-4D-2 — One prototype only, the engine mount being revised to eliminate the down thrust position.
JN-4H — two-seat advanced trainer biplane, 929 built for the U.S. Army. Notable for introducing the use of the Hispano-Suiza 8 V-8 engine for greater power and reliability.
JN-4HT — Two-seat dual-control trainer version.
JN-4HB — Bombing trainer version.
JN-4HG — Gunnery trainer version.
JN-4HM — communications conversion of JN-4HT, powered by Wright-Hisso E 150 hp (112 kW); six converted. Used to fly the first US Air Mail (May–August, 1918)
JN-5H — One-off advanced trainer biplane, only one was built.
JN-6 — Improved version of JN-5 trainer biplane series notably used four ailerons. A total of 1,035 built for the US Army and five for the U.S. Navy.
JN-6H — Improved version of the JN-6.
JN-6BH — Bomber trainer version.
JN-6HG-1 — Two-seat dual-control trainer version; 560 built from JN-6 production, 34 for US Navy.
JNS ("standardized") — During the postwar years of the early 1920s, between 200 and 300 U.S. Army aircraft were upgraded to a common standard of equipment and modernized.
"Specials" and one-offs
Allison Monoplane — Conversion of JN-4 (Can) G-CAJL by the Allison Company, Kansas, that mounted a parasol wing in place of the biplane configuration; only one conversion made.
Curtiss Special (1918) — A smaller, custom-built single-seat variant for Katherine Stinson, powered by a 100 hp (74.5 kW) OXX-6.[N 6]
Ericson Special Three — Some reconditioned aircraft built by Canadian Aeroplanes Ltd. were fitted with a third cockpit.
Hennessey Monoplane —  1926 monoplane conversion by James R. Hennessey, three-place transport; 90 hp (67 kW) Curtiss OX-5; span: 36 ft (11 m) length: 25 ft (7.6 m).
Severski 1926 biplane — A JN-4 modified with a roller / ski undercarriage, one experimental aircraft converted by the Seversky company.[N 7]
Sperry Monoplane — Conversion offered by the Sperry Company that mounted a parasol wing in place of the biplane configuration.
Twin JN — Enlarged twin-engined version of the JN-4, powered by two OXX-2 piston engines. Built in 1916 as the JN-5 for an observation role, among the many other modifications was an enlarged wingspan and new rudder adapted from the Curtiss Model R-4. Two of the series saw action with the US Army on the Mexican border in 1916–1917. A total of eight Twin JNs were built, with two in US Navy service.
Converted JN-4 ambulance, operated by the Camp Taliaferro medical teams, c. 1918
JN-4D U.S. Army Air Corps "2525" on display at the Call Aviation Field Memorial Exhibit at Kickapoo Air Park in Wichita Falls, Texas. It is flown on the first Saturday of each month, weather permitting.
For comparison, this 1923 Standard J shows its similarity to the JN-4's appearance.
The Cradle of Aviation Museum on Long Island has two Jennys on display. One is the aircraft owned by Charles Lindbergh in which he barnstormed long before his transatlantic flight. Lindbergh purchased this aircraft in Americus, Georgia for $500 in May 1923, and sold it to a flying student of his in Iowa the following October. It was restored by the late George Dade in the 1970s and is on loan from the Long Island Early Fliers Club.
A JN-4D built in 1917 has been fully restored to flying condition and is on display, as well as being available for flights at the Golden Age Air Museum at Grimes Airport, Bethel, Pennsylvania.
A JN-4D built in 1918 fully restored to flying condition and is on display at the Flying Heritage Collection at Paine Field in Everett, WA.. It is U.S. Army Air Corps "3712" based at March Field, CA.
JN-4H, restored as U.S. Navy 6226 (ex-USAAS "38262"), powered by a rare Hispano-Suiza 8, V-8 engine, on display at the Old Rhinebeck Aerodrome in Rhinebeck, New York. It is still flightworthy and frequently flown during the ORA facility's weekend airshows.
The "Inverted Jenny" (C-3a) is a 24 cent 1918 US Air Mail postage stamp printing error in which the blue central vignette of US Army Curtiss JN-4HM #38262, the nation's first mailplane, appeared as "inverted" on a single sheet of 100 stamps owing to an inadvertent error made by the operator of a hand rolled spider press by printing the red frame impression upside down after the vignettes had already been printed on the sheet on another press. As the Jenny vignette was only inverted on one sheet, this stamp represents the rarest and most valuable known USPOD printing error of all time. A single example (sheet position 57) sold at auction in 2007 for $977,500.00.
This 1917 Curtiss Jenny still flies on occasion. Its home base is the Call Memorial Museum in Wichita Falls, Texas.
Broadcast on April 15, 1987, by PBS, the National Geographic special entitled "Treasures from the Past" featuring the restoration and first flight by Ken Hyde of a JN-4D that would go on to win the "Lindy Award" at the EAA AirVenture Oshkosh '87.
Notable musician Al Stewart refers to the Jenny in his song "The Immelman Turn" (2005) in which a barnstorming acrobat falls to his death from a Curtiss Jenny attempting the maneuver in a 1923 airshow.
On the TV Show "The UNIT" Season 4: Episode 11 "Switchblade", New character Joss Morgan of Morgan Aviation Company owns a 1917 Curtis "Jenny" and cracks a piston and ends up showing up at the UNITS front fake aviation business looking for help fixing it. She meets her future Husband UNIT Member Sgt. 1st Class Charles "Carlito" Grey about the piston. He then gets to buy her a drink for telling her what plane the piston was from. He then trades the broken piston for a real piston from the National Air Museum through a friend for his Colt BBQ gun. She was going to show him the "Outside Loop Maneuver".
^Both the US Army version and the Canadian derivative for the Royal Flying Corps were known as JN-4s. In order to differentiate between the types, unofficially the RFC designation was the JN-4 (Canadian).
^Surplus JN-4s typically fetched between $200–$500, depending on condition.
^The front cockpit that was normally for the student in military training was usually used for passengers in postwar joy rides, so that the pilot could keep an eye on his paying customer/s.
^The JN-4 Canuck was often chosen for barnstorming as the lighter, more responsive and more economical variant was also in large supply.
^Quote: "A JN-4-d plane was used; speed was successful, transmitting about 3 miles from plane to plane and was also received from ground to plane, and vice versa." 
^Stinson's aircraft built to her specifications was used for fundraising tours for the American Red Cross. During exhibition flights in Canada, she set a Canadian distance and endurance record, and made the second air mail flight in Canada between Calgary and Edmonton, Alberta. A replica is at the Alberta Aviation Museum.
^"Report of the Chief Signal Officer to the Secretary of War, October 15, 1919". Annual Report, War Department, 1919, pp. 262–263.
^"Handwritten letter, dated August 18, 1917, from Western Electric Co (Bell Labs) design engineer Lewis M. Clement to Vesta L. Clement, his wife, with a detailed first person account of the first successful test of 'plane-to-plane' and 'plane-to-ground' radiotelephony from JN-4-d airplanes in flight conducted that day at Langley Field, VA." The Cooper Collection of U.S. Aviation History (Private collection: original letter location), Ardmore, Pennsylvania.